(1) Field of the Invention
The invention generally relates to means and methods of preventing or reducing stucco cracks at door and window corners. More specifically, disclosed embodiments include corner elements or work pieces that integrate into a stucco installation and then evenly dissipate differential building movement.
(2) Description of the Related Art
Lath and stucco material combine to form an integral unit. First, walls of a structure are waterproofed during the lathing process with two layers of grade D paper or equivalent. Next, a metal lath or chicken wire is installed and secured with 1¼″ staples or other appropriate fasteners with the intended purpose of providing an ideal surface to support the plaster material. Stucco usually comprises a three coat system with a thickness of ⅞″ and is applied in the following sequence: scratch coat, brown coat and finish coat. Stucco is applied as a wet cementitious material that may crack during the drying process, or more often may crack as a result of building settlement or earth movement. Cracks most often develop at or near window and door corners where building movements become unevenly dispersed.
The prior art of control joints on exterior stucco walls is often used in an effort to minimize cracks in large or long stucco panels. Although not intentionally created for this purpose, control joints can also be used at doors and windows. However, control joints add time and expense during the stucco installation process adding several hours of labor per control joint to ensure proper installation. Control joints are visible upon completion of the stucco system and may reduce the design appeal of the stucco, thereby deterring some builders or architects from using stucco. Thus, control joints represent a shortfall in the art.
The prior art often resorts to a synthetic material used in acrylic finish coats which may stretch to some extent with building movement in an effort to reduce the likelihood of hairline cracks. Unfortunately, exterior acrylic finish coats often fail to exhibit the necessary flexibility to remain intact since most structural cracks develop in the scratch coat and move outward toward the finished surface. Therefore, the superficial nature of acrylic finishes alone cannot hide or prevent most structural cracks. Consumers are also discouraged from incorporating an acrylic finish application into a stucco system due to the high cost associated with synthetic material.
More recently, the prior art involving new base and mesh systems have been advocated by various stucco trade organizations that employ polymer-modified coatings which are applied over the brown coat. Such solutions deal with the general field of stucco walls and teach away from specially addressing door or window corners. It is important to note that using a reinforcing fiber mesh embedded in a base coat is very costly, since it requires another coat of material to be applied over the entire structure. This option is often presented to customers by plastering contractors, although due to the additional time and cost associated with this system, it is usually declined. When accepted, the success of the mesh system is most effective in controlling minor cracks on large, uninterrupted surfaces and not at locations of most stress, specifically openings with square corners. See Base and Mesh Systems for Crack Reduction (March 2011) Stucco Manufactures Association, Newport Beach, Calif.
U.S. Pat. No. 1,355,756 issued on Oct. 12, 1920 to Earley is entitled “Flexible Joint for Stuccoed Buildings” discloses a spacer system to create an air space near doors and windows to allow surrounding stucco work to move without directly pressing upon stucco applied over door or window joints. The product is very similar to a casing bead around a frame, in that it functions more as a plaster stop and does not distribute the concentration of stress that accumulates and is released at the corners of windows and doors; thus cracks still form.
U.S. Pat. No. 4,651,488 issued on Mar. 24, 1987 to Nicholas et al is entitled “Expansion Joint for Plaster Walls” and discloses a unitary extruded plaster screed expansion joint system to reduce stucco cracks.
U.S. Pat. No. 5,699,638 issued on Dec. 23, 1997 to Maylon is entitled “Stucco Arch Casing Bead” and discloses an arch casing bead with a mounting flange and other features to facilitate the construction of stucco archways. Maylon fails to teach or consider the reduction of stucco cracks as Maylon is used to create a smooth surface for aesthetic and architectural purposes. The structure of Maylon would not work for reducing stucco cracks, but is merely used as a mold system.
U.S. Pat. No. 5,820,958 issued on Oct. 13, 1998 to Swallow discloses an elastic membrane with a pair of parallel strips. Swallow presents an interior cover-up adhesive to cover interior cracks prior to application of spackle or dry wall mud. Swallow merely spans both ends of a drywall repair and fails to consider the issue of preventing future cracks on stucco. The physical device of Swallow bears no resemblance to the disclosed embodiments.
U.S. Pat. No. 7,874,123 issued on Jan. 25, 2011 to Mariarz is entitled “Stop Bead for Separating Stucco Material from a Frame of a Window or Door” and discloses a slight variation to the traditional L-Bead system used to reduce the time and cost of applying stucco near a door or window. Here again, no corner provisions are considered, as the Mariarz disclosure is concerned with the speed of stucco application and not the reduction of subsequent cracks. Thus, there is a long felt need in the art for the embodiments of the present invention.